Runemark, H 1956: Studies in Rhizocarpon. I. Taxonomy of the yellow species in Europe. Opera Botanica 2(1): 1-152.
Thallus 0.5-5 cm in diam. Areolae and apothecia close together forming a continuous thallus or dispersed. Prothallus black, distinct. Primary areolae rarely subdivided.
Areolae 0.4-2.0 mm in diam., 0.2-0.7 mm thick, usually strictly angular, often with concave sides, plane to slightly convex, whitish-yellow, surface farinose, matt; cortex 20-50 µ thick; medulla white.
Apothecia 0.3-1.0 mm in diam., 0.2-0.8 mm thick, roundish to roundish angular, +/- plane to slightly convex, often with a distinct margin. Cortex cells of the epitheciumbrownish-red, K+ reddish-violet. Subhymenium 100-250 µ thick, brown, K-k, surrounded by medullary tissue. Hymenium 140-200 µ thick, +/- colourless, uppermost part reddish, K+ reddish-violet; apical cells of paraphyses clavate, transparent. Epihymenium indistinct. Asci clavate ca. 100-150 X 25-40 µ containing 8 spores. Spores muriform, with many septa, 25-40 X 12-17 µ.
Lichen substances. Rhizocarpic acid and an unknown substance. Reacitons: K-, Pd+ faintly reddish-violet or Pd-, I+ intensely blue.
Ca. 35 collections examined.
Variability.Rh. saanaënse is a rather variable species. It varies in size from 0.5 cm up to 5 cm. The size of the areolae and apothecia is also rather variable. The spore size and the multitude of septa in the spores are also variable within wide limits.
Infraspecific units described in literature:
f. mendozae RÄSÄNEN 1948 p. 383.—Orig. coll. Argentina. Luján, Quebrada de la Manga 2800-3000 m 1939 Ruiz Leal.—Type not seen by me.
v. dispersa RÄSÄNEN 1949 b p. 86.—Orig. coll. N. Greenland. Centrum-ön 1917 Wulff (H holotype).—var. dispersum is described on a very small, but typical specimen of Rh. saanaënse. Probably it is only a modification caused by hard conditions.
Taxonomic remarks.Rh. saanaënse is characterized by its angular, +/- undivided, whitish areolae, and by its distinctly muriform spores. From the other whitish species, Rh. atroflavescens, it is easily distinguished by its undivided areolae, and by its muriform spores. Whitish species of Rh. sublucidum may sometimes be difficult to distinguish from Rh. saanaënse.
Rh. saanaënse has been described (by RÄSÄNEN) under different names. The units described are listed below with a short comment.
Rh. fruticosum is described on a small specimen of Rh. saanaënse, growing on bark of Rhododendron. It is characterized by relatively small spores. Together with other yellow Rhizocarpon species, Rh. saanaënse is sometimes found on Rhododendron stems in the Alps.
Rh. riparium v. subgeronticum is described on a specimen of Rh. saanaënse with small, convex areolae and large multi-septate spores.
Rh. riparium v. pseudoviride f. dealbatum is described on a somewhat destroyed specimen, probably belonging to Rh. saanaënse, with rather multi-septate spores.
Rh. riparium v. ursinum is described on a specimen of Rh. saanaënse with small plane areolae, small apothecia, and large, multi-septate spores.
Ecology. Usually on slightly calcareous rock in the alpine belt or on rocks on the shores of lakes (also below the alpine belt). Also found on Rhododendron stems in the Alps.
Distribution.Rh. saanaënse occurs in the Arctic, the Scandinavian Mts., and in the Alps. I have also seen a specimen from the Yünnan Mts.